U.S. patent application number 13/639877 was filed with the patent office on 2013-02-21 for lighting device having a smooth cut-off.
This patent application is currently assigned to Koninklijke Philips Electronics, N.V.. The applicant listed for this patent is Denis Fournnier, Matthias Jouffrieau. Invention is credited to Denis Fournnier, Matthias Jouffrieau.
Application Number | 20130044479 13/639877 |
Document ID | / |
Family ID | 44148894 |
Filed Date | 2013-02-21 |
United States Patent
Application |
20130044479 |
Kind Code |
A1 |
Jouffrieau; Matthias ; et
al. |
February 21, 2013 |
Lighting device having a smooth cut-off
Abstract
The invention relates to a lighting device comprising:--at least
one light source (11);--a reflective member (20) comprising a
reflective surface (22) and an edge (21) ("first edge") forming a
light cut-off of light rays passing in a region adjacent to this
first edge (21);--a light-modifying member (30) adapted to modify
lighting feature(s) of light rays and having an edge ("second
edge"). The light-modifying member (30) extends from the reflective
member (20) to this second edge (31) over a surface area defined to
receive a part of the light rays passing in said region. The second
edge is designed such that, among said part of light rays, the
light-modifying member (30) modifies proportionally more light rays
passing proximate the first edge than light rays passing less
proximate the first edge (21). The invention relates also to said
light-modifying member (30) per se.
Inventors: |
Jouffrieau; Matthias; (Lyon,
FR) ; Fournnier; Denis; (Lyon, FR) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Jouffrieau; Matthias
Fournnier; Denis |
Lyon
Lyon |
|
FR
FR |
|
|
Assignee: |
Koninklijke Philips Electronics,
N.V.
Eindhoven
NL
|
Family ID: |
44148894 |
Appl. No.: |
13/639877 |
Filed: |
April 1, 2011 |
PCT Filed: |
April 1, 2011 |
PCT NO: |
PCT/IB11/51399 |
371 Date: |
October 8, 2012 |
Current U.S.
Class: |
362/235 |
Current CPC
Class: |
F21V 7/048 20130101;
F21Y 2105/10 20160801; F21Y 2115/10 20160801; F21V 11/00 20130101;
F21V 3/04 20130101; F21V 7/06 20130101; F21V 13/10 20130101; F21V
13/04 20130101 |
Class at
Publication: |
362/235 |
International
Class: |
F21V 13/08 20060101
F21V013/08; F21V 7/00 20060101 F21V007/00 |
Foreign Application Data
Date |
Code |
Application Number |
Apr 9, 2010 |
EP |
10305371.6 |
Claims
1. A lighting device comprising: at least one light source; a
reflective member comprising a reflective surface and a first edge
forming a light cut-off of light rays passing in a region adjacent
to said first edge; a light-modifying member configured to modify
one or more lighting feature of light rays, having a second edge,
the light-modifying member extending from the reflective member to
said second edge over a surface area defined to receive a part of
the light rays passing in said region and not reflected by the
reflective surface, wherein the second edge is configured such
that, among said part of light rays, the light-modifying member
modifies proportionally more light rays passing proximate to said
first edge than light rays passing less proximate said first
edge.
2. The lighting device according to claim 1, wherein the light
modifying member extending along at least a part of the first edge
or along a line on the reflective surface equidistant to the first
edge.
3. The lighting device according to claim 1, wherein the light
modifying member comprises a plurality of light modifying elements
delimited by said second edge and spaced apart one to the other by
respective light transparent regions, wherein each light
transparent region has a first end and a second end opposite to the
first end, wherein the first end: closer to the reflective surface
than the second end, and smaller than the second end.
4. The lighting device according to claim 3, wherein the shape of
at least one light transparent region is an entire triangle or a
triangle with a rounded vortex which is the first end.
5. The lighting device according to claim 3, wherein at least a
part of one light transparent region is progressively wider from
its first end to its second end.
6. The lighting device according to claim 3, wherein the light
modifying comprises a base fixed or attached or assembled to the
reflective member, the light modifying elements extending from the
base outwardly from the reflective member.
7. The lighting device according to claim 3, wherein at least one
light modifying element has a first end and a second end opposite
to the first end, wherein the first end is: closer to the
reflective surface than the second end, and greater than the second
end.
8. The lighting device according to claim 7, wherein the shape of
at least one light modifying element is an entire triangle or a
triangle with a rounded vortex which is the second end.
9. The lighting device according to claim 3, wherein the light
modifying elements extend outwardly from the reflective member
according to angles in the range between 0.degree. and 90.degree.
with respect to a main light direction, the main light direction
being the direction of emitted light rays along which the intensity
of the light is maximum.
10. The lighting device according to claim 3, comprising an array
of light sources, wherein these light sources are LED chips having
a width "e" and spaced apart one to the other over a distance "h",
and wherein at least a part of the light modifying elements extend
outwardly from the reflective member over a length of about "h" and
have widths of about "e".
11. The lighting device according to claim 3, wherein the surface
area of each light-modifying element is similar to the surface area
of each gap.
12. The lighting device according to claim 1, wherein the quantity
of non-reflected rays emitted by one of said light source(s) over a
first direction is significantly lower than the quantity of
non-reflected light emitted by the same light source(s) over a
second direction, wherein a light cut-out exists between these two
directions, and wherein the second edge of the light modifying
member is designed to smooth progressively this light cut-off.
13. The lighting device according to claim 1, comprising a
plurality of light sources wherein: the quantity of non-reflected
light emitted by at least one light source over a first direction
is different from the quantity of non-reflected light emitted by
this at least one light source over a second direction, by a first
differential value; the quantity of non-reflected light emitted by
at least one other light source over the first direction is
different from the quantity of non-reflected light emitted by this
at least one other light source over the second direction, by a
second differential value; wherein the first differential value is
significantly greater than the second differential value and a
light cut-out exists between these two directions; and wherein the
second edge of the light modifying member is designed to smooth
progressively this light cut-off.
14. The lighting device according to claim 1, wherein the light
modifying member absorbs and/or diffuses said part of light.
15. A light modifying member arranged to be fixed, attached or
assembled to a reflective member of a lighting device, wherein the
lighting device comprising: at least one light source; said
reflective member comprising a reflective surface and an edge
("first edge") forming a light cut-off of light rays passing in a
region adjacent to this first edge; wherein the light-modifying
member is adapted to modify lighting feature(s) of light rays,
having an edge ("second edge") such that the it extends from the
reflective member to this second edge over a surface area defined
to receive a part of the light rays passing in a region adjacent to
the first edge and non reflected by the reflective surface, wherein
the second edge is designed such that, among said part of light
rays, the light-modifying member modifies proportionally more light
rays passing proximate the first edge than light rays passing less
proximate the first edge.
Description
TECHNICAL FIELD
[0001] The invention relates to a luminaire or a lighting device
comprising: [0002] at least one light source, such as one or
several LEDs; [0003] a reflector (or reflective member) comprising
a reflective surface and a first edge, the first edge forming a
light cut-off of light rays passing proximate this first edge--the
first edge defines typically the light outlet of the reflector.
[0004] The light source(s) is usually located within the reflector,
the reflector being arranged to reflect the light emitted by the
light source(s) in order to direct the emitted rays into specific
directions to illuminate a region area limited by said light
cut-off.
BACKGROUND OF THE INVENTION
[0005] Problems encountered with such reflectors are the contrast
of the light that is sometimes too high at the limit or edge of the
region to illuminate and/or the light is not uniform near the
cut-off direction, especially when a plurality of punctual light
sources is used. As a consequence the lighting effects may be
unpleasant and/or non aesthetic, especially problematic for Accent
Lighting or Spot Lighting applications.
[0006] It is known to use some lenses as accessories, to smooth the
light beam near the cut-off direction, those lenses being typically
provided at the outlet of the reflector.
[0007] For example U.S. Pat. No. 4,506,316, U.S. Pat. No. 5,199,787
and U.S. Pat. No. 7,040,789 disclosed disk-shaped lenses provided
with an annular portion having a plurality of tapered optical
elements to deviate the rays passing proximate the light cut-off
directions.
[0008] However, the limits of the region to be illuminated may be
not sufficiently controlled when using this technique and the
lighting efficiency may be not optimized.
SUMMARY OF THE INVENTION
[0009] A purpose of the invention is to smooth the light cut-off
region in the area to illuminate, created by said edge of the
reflector, while optimizing the control over the size and shape of
the area to be illuminated and limiting the light losses.
[0010] A "Light cut-off region" means the region(s) located: [0011]
in the area to illuminate; and/or [0012] in a volume crossed by
non-reflected light rays, where the light is so disturbed by a
light cut-off edge of the reflective member that lighting
inhomogeneities can be visible for an observer.
[0013] Another purpose of the invention is to remove or decrease
these unpleasant light inhomogeneities, in the light cut-off region
of the area to illuminate, which appear especially when a plurality
of individual lights sources (e.g. a array of LEDs) is used.
Indeed, due to these discontinuities in the light source, the light
cut-off region exhibits some non-continuous light sub-regions (i.e.
some light steps), each having a specific light-cut-off with the
adjacent sub-regions.
[0014] Another purpose of the invention is to decrease the light
contrast in the light cut-off region.
[0015] To overcome these problems, the invention proposes,
according to a first aspect, a lighting device comprising: [0016]
at least one light source; [0017] a reflective member comprising a
reflective surface and an edge ("first edge"), the first edge
forming a light cut-off of light rays passing in a region adjacent
to this first edge; [0018] a light-modifying member adapted to
modify lighting feature(s) of light rays.
[0019] According to a first embodiment of the invention, the
light-modifying member has an edge ("second edge"), and the
light-modifying member extends from the reflective member to this
second edge over a surface area defined to receive a part of the
light rays: (i) passing in said region; and (ii) non reflected by
the reflective member. The second edge is designed such that, among
said part of light rays, the light-modifying member modifies
proportionally more light rays passing proximate the first edge
than light rays passing less proximate the first edge.
[0020] In other words, said second edge is designed such that
closer said light rays pass to the first edge greater the quantity
of modified light rays. Accordingly, the intensity of light changes
more progressively in the light cut-off region when using the
light-modifying member. As a consequence, this light-modifying
member smoothes said light cut-off.
[0021] Advantageously, said region adjacent to the first edge is a
light cut-off region.
[0022] Moreover the light-modifying member acts only on the rays in
this light cut-off region, and leaves the other rays outputting the
lighting device without any disturbance. Therefore this
light-modifying member does not modify most of the light emitted by
the lighting device, and the overall efficiency of the lighting
device is optimized accordingly.
[0023] Moreover, the invention allows an easy control of the light
modification, by simply adapting the design or shape of the second
edge of the light-modifying member, without modifying the
reflective member.
[0024] Optionally the light-modifying member extends along, covers
or is adjacent to at least a part of the first edge. This is
equivalent to a replacement of this at least part of the first edge
by the second edge, without modifying the integrity of the
reflective member, but only by adding this light-modifying member
to the lighting device. Therefore the light cut-off can be easily
smoothened without modifying or changing the reflector and without
necessarily removing the reflective member from the holding
structure to which it may be attached. This is especially
advantageous if the reflector is already in a place and not easily
accessible and/or is not easily dismountable.
[0025] Alternatively the light-modifying member may extend along a
line on the reflective surface defined as being equidistant to the
first edge. This particular embodiment can allow providing the
light-emitting member inside the reflective member, and being
therefore less visible than in the previous embodiment. The
light-modifying member can be attached directly within the
reflective member or between two sub-portions of the reflective
member.
[0026] According to a second embodiment of the invention, taken
sole or in combination with said first embodiment, the light
modifying member comprises a plurality of light modifying elements
delimited by the said second edge and spaced apart one to the other
by respective light transparent regions, wherein each light
transparent region has a first end and a second end opposite to the
first end, wherein the first end is: [0027] closer to the
reflective surface than the second end, and [0028] smaller than the
second end.
[0029] The shape of at least one of said light transparent regions
is an entire triangle or a triangle with a rounded vortex which is
the first end. Alternatively or in combination, at least one said
transparent regions is progressively wider from its first end to
its second end.
[0030] Optionally, the light modifying member may comprise a base
fixed or attached or assembled to the reflective member, the light
modifying elements extending from the base outwardly from the
reflective member.
[0031] According to a third embodiment of the invention, taken sole
or in combination with said first and/or second embodiments, at
least one light modifying element has a first end and a second end
opposite to the first end, wherein the first end is: [0032] closer
to the reflective surface than the second end, and [0033] greater
than the second end.
[0034] The overall shape of at least one of said light modifying
elements is entirely triangular or triangular with the second end
which is rounded. Alternatively or in combination, the light
modifying elements extend outwardly from the reflective member
according to angles in the range between 0.degree. and 90.degree.
with respect to a main light direction, the main light direction
being the direction along which the intensity of the light emitted
by the light source(s) is maximized with respect to the other
directions.
[0035] Optionally, the lighting device comprises an array or a
array of light sources, wherein light sources are chips of LED
having a width "e" and spaced apart one to the other over a
distance "h", at least a part of said light modifying elements
extending outwardly from the reflective member over a length of
about "h" and have widths of about "e".
[0036] Optionally, the surface area of each light-modifying element
is similar to the surface area of each gap. As a consequence, the
lighting is more homogeneous around the center of the illuminated
surface area.
[0037] Optionally, the lighting device is arranged such that the
quantity of non-reflected rays emitted by one of said light
source(s) over a first direction is significantly lower than the
quantity of non-reflected light emitted by the same light source(s)
over a second direction, wherein a light cut-out exists between
these two directions, and wherein the second edge of the
light-modifying member is designed to smooth progressively this
light cut-off.
[0038] Optionally, the lighting device comprises a plurality of
light sources and is arranged such that: [0039] the quantity of
non-reflected light emitted by at least one light source over a
first direction is different from the quantity of non-reflected
light emitted by this at least one light source over a second
direction, by a first differential quantitative value; and that
[0040] the quantity of non-reflected light emitted by at least one
other light source over the first direction is different from the
quantity of non-reflected light emitted by this at least one other
light source over the second direction, by a second differential
quantitative value;
[0041] wherein the first differential quantitative value is
significantly greater than the second differential quantitative
value and a light cut-out exists between these two directions; and
wherein the second edge of the light modifying member is designed
to smooth progressively this light cut-off.
[0042] Optionally the light modifying member absorbs and/or
diffuses said part of light to prevent it to pass proximate the
first edge.
[0043] According to a second aspect, the invention proposes a light
modifying member arranged to be fixed, attached or assembled to a
reflective member of an lighting device, wherein the lighting
device comprising: [0044] at least one light source ; [0045] said
reflective member comprising a reflective surface and an edge
("first edge") forming a light cut-off of light rays passing in a
region adjacent to this first edge; wherein the light-modifying
member is adapted to modify lighting feature(s) of light rays,
having an edge ("second edge") such that the it extends from the
reflective member to this second edge over a surface area defined
to receive a part of the light rays passing in a region adjacent to
the first edge and non reflected by the reflective surface, wherein
the second edge is designed such that, among said part of light
rays, the light-modifying member modifies proportionally more light
rays passing proximate the first edge than light rays passing less
proximate the first edge.
BRIEF DESCRIPTION OF DRAWINGS
[0046] FIG. 1 is an exploded view of a lighting device according to
the invention.
[0047] FIG. 2A is a perspective view of a light-modifying member
according to the invention.
[0048] FIGS. 2B and 2C are top views of a part of light-modifying
members according to, respectively, two particular embodiments of
the invention.
[0049] FIGS. 3, 4, 5 and 6 are perspective views of a part of a
lighting device comprising a light-modifying member according to,
respectively, a first, second, third and fourth embodiments of the
invention, and showing at least a part of the emitted non-reflected
light rays incident onto an element of these light-modifying
members.
[0050] FIG. 7A is a top view of a array of nine LEDs.
[0051] FIG. 7B is a side view of a part of a light-modifying member
according to the invention.
[0052] FIG. 8 is a schematic illustration of how the
light-modifying member can mask an array of three LEDs.
[0053] FIG. 9A, 9B, 9C are first, second and third perspective
views of an lighting device according to the invention.
[0054] FIG. 10A is a graph of normalized intensities (y-axis) of
light output measured from the lighting device according to FIG. 1
but without the light-modifying member, according to different
angles (x-axis), the zero-reference of these angles corresponding
to the main optical axis of the lighting device.
[0055] FIG. 10B is the part 3 of the graph of FIG. 10A, in
comparison with the part of another graph relating to the same
lighting device but with the light-modifying member.
DETAILED DESCRIPTION OF THE INVENTION
[0056] FIG. 1 shows a light device 40 according to the invention
comprising: [0057] a light source assembly 10; [0058] a reflector
20 comprising a reflective surface 22 and a first edge 21; [0059] a
light-modifying member 30 adapted to modify lighting feature(s) of
light rays.
[0060] The light source assembly 10 may comprise one or a plurality
of light source(s). The plurality of light sources may extend over
a line, a plane or a volume. A light source may be any kind of
light source, such as an incandescent lamp, halogen lamp, a
high-intensity discharge (so-called HID) lamp or a light-emitting
diode (LED). The light source assembly 10 may comprise a unique or
a plurality of support(s) of the light source(s) provided with
electrical and/or electronic path to a current supply and
optionally to a light controller. The circuit board may comprise
this lighting controller. A heat sink or nay other cooling system
may be provided beneath the LEDs or the circuit board, to dissipate
the heat from the LEDs. The light source assembly 10 may further
comprise primary optics, such as lenses, designed to redirect the
light emitted by the light source(s). The light source assembly 10
may further comprise some additional components, such as for
example a diffusing element (e.g. a diffusing coating or film, or a
diffusing panel) provided on the light source(s) or between the
light source and the primary optics or on the primary optics.
[0061] In the example depicted by FIG. 1, the light source assembly
10 comprises a array of LEDs, fixed to a circuit board and/or to a
heat sink, and covered by a primary optical element (comprising a
plurality of elementary lenses). This light source assembly 10 may
be arranged as a closed pack solution, i.e. a solution which
provides a compact light source assembly 10. Such a closed pack
solution may be made by using the technique reflow soldering to
mount the LEDs onto the circuit board or onto the heat sink. The
array may be square, rectangular, round, ellipsoidal or of any
other configuration. Each LED might be seen as a light point or as
a small light spot. This closed pack solution allows having a high
density of light emission over a limited surface, leading to a more
compact lighting device 40.
[0062] The reflector 20 may be closed or opened.
[0063] In the example of FIG. 1, the reflector 20 is closed and
have a main optical axis 100.
[0064] The main optical axis 100 can be defined as an axis of
symmetry of the reflector 20 or as an axis of symmetry of the light
or as an axis along which the intensity of the emitted light is
maximum. The main optical direction 100 is the same as the main
optical axis 100, but directed outwardly from the light
sources.
[0065] This reflector 20 might be of any shape. For example, the
reflector 20 may be generally hemispherical, parabolic, tapered.
The reflector 20 may have a square, rectangular, round,
ellipsoidal, triangular, or any other cross-section shape (taken
perpendicular to the main optical axis 100). The reflective face 22
of the reflector 20 may be continuous or made of a plurality of
flat faces (as depicted in FIG. 1).
[0066] In the example depicted by FIG. 1, the light outlet of the
reflector 20 is limited by the first edge 21. This light outlet may
have any shape, e.g. a square, rectangular, round, ellipsoidal or
triangular shape. Optionally, a flange 23 may extend from the first
edge 21 transversal to and outwards from the main optical axis
100.
[0067] The bottom portion 24 of the reflector 20 may be provided
with an aperture to receive the light source assembly 10 within.
Alternatively, the light source assembly 10 may be provided in the
reflector 20 and through holes are provided in the bottom portion
24 of the reflector 20 to allow the electrical connection to the
light source assembly 10.
[0068] The light-modifying member 30 may extend along at least a
part of the first edge 21 (as depicted in FIG. 1) and therefore
around at least a part of said light outlet. Optionally, another
reflective member (not shown) may be added onto the reflector 20,
the light-modifying member 30 being located at the interface.
[0069] Alternatively, the light-modifying member 30 may extend
along a line on the reflective surface 22 defined to be equidistant
to the first edge 21 (not shown).
[0070] The light-modifying member 30 may be an accessory added to
the lighting device 40 or may be integral with the reflector
20.
[0071] The light-modifying member 30 may be fixed or attached to
the reflector 20 by gluing, by mechanical fixation means (e.g.
screws, bolt/nuts), by soldering, or any other relevant kind of
means for attaching of fixing the light-modifying member 30.
[0072] The light-modifying member 30 is adapted to modify lighting
characteristic(s) of a part of the light rays passing proximate the
first edge 21 of the reflector, in a light cut-off region.
[0073] To this effect, the light-modifying member 30 may have light
absorbing, diffusing and/or reflective properties. The material
chosen for such member 30 may be a translucent polymer, clear
polymer with at least one textured surface, clear glass with a
textured area, or a combination thereof.
[0074] The light-modifying member 30 has an edge 31 ("second edge")
designed such that said part of light rays modified by the
light-modifying member 30 is greater for some light rays passing
more proximate the first edge 21 than some other light rays passing
less proximate the first edge 21. Preferably, the light-modifying
member 30 comprises a plurality of light-emitting elements 31 which
extends in the light cut-off region of the first edge 31 so as to
smooth the downstreamed light in this region.
[0075] FIG. 2 shows an example of such a light-modifying member 30
according to the invention, which is arranged to be placed along or
in vicinity to a rounded first edge 21 of the reflector 20. This
particular light-modifying member 30 comprises a base 33 to be
attached to the flange 23 of the reflector 20. For example, a
method of attaching the light-modifying member 30 to the flange 33
is to provide some protrusions, rods or rivets equally distributed
over the surface of the flange 23 and corresponding through holes
in the base 33 to receive this protrusions. Once this montage is
performed, a way to seal or fix the light-modifying member 30 onto
the flange 23 can be done, by for instance soldering the
protrusions to the base 33 or providing a kind of blot on the end
portions of the protrusions.
[0076] Preferably, the light-modifying member 30 further comprise
light-modifying elements 32 extending from the base 33 transversal
to and towards the main optical axis 100 over a region relating to
the light cut-off region of the first edge 21. The edge of the
light-modifying elements 32 is said second edge 31.
[0077] The light-modifying elements 32 are preferably separated by
some gaps 39 or light transparent regions (which is for example a
transparent solid material such as glass) having respectively a
first end 39' and a second end 39'', wherein the first end 39' is:
[0078] closer to the reflective surface 22 (or to the base 33) than
the second end 39'', and [0079] smaller than the second end
39''.
[0080] As a consequence, less non-reflected light rays pass through
the first end 39' than light rays passing through the second end
39''. The light in the light cut-off region is therefore smoothened
downstream the light-modifying element 30.
[0081] Preferably, each gap 39 is progressively wider from the
first end 39' to the second end 39''. The smoothing of the light in
the light cut-off region is improved accordingly.
[0082] As an example, depicting by FIG. 2B or FIG. 2E, at least one
light gap 39 is shaped as an entire triangle.
[0083] As another example, depicting by FIG. 2C, at least one light
gap 39 is shaped as a triangle with a rounded vortex as the first
end 39'.
[0084] As another example, depicted by FIG. 2E, at least one
light-modifying element 32 has a rounded end portion 31'' limited
by a portion of a circle.
[0085] Other kinds of shapes of gaps 39 can be designed by the
designers of the light-modifying member 30 so as to reach a desired
lighting effect.
[0086] Alternatively or in combination of the embodiment with gaps
39, at least one light modifying element 31 may have a first end
31' and a second end 31'' opposite to the first end 31', wherein
the first end 31' is: [0087] closer to the reflective surface 22
(or to the base 33) than the second end 32'', and [0088] wider than
the second end 32''.
[0089] As a consequence, there are more light rays modified by the
first end 32' than light rays modified by the second end 32''. The
light in the downstream light cut-off region is therefore
smoothened.
[0090] Preferably, each light-modifying element 32 is progressively
less wide from the first end 32' to the second end 32''. The
smoothing of the light in the light cut-off region is improved
accordingly.
[0091] As an example, depicted by FIG. 2B, at least one
light-modifying element 32 is shaped as an entire triangle.
[0092] As another example, depicted by FIG. 2C, at least one
light-modifying element 32 is shaped as a triangle with a rounded
vortex as the second end 31''.
[0093] As another example, depicted by FIG. 2D, at least one
light-modifying element 32 is rounded-shaped, whose the end portion
31'' is limited by a portion of a circle.
[0094] As another example, depicted by FIG. 2E, at least one
light-modifying element 32 has a rounded end portion 31'' limited
by a portion of a circle.
[0095] Other kinds of shapes of light-modifying elements 32 can be
designed by the designers of the light-modifying member 30 so as to
reach a desired lighting effect.
[0096] Preferably, the light-modifying elements 32 extend outwardly
from the reflective member 22 according to angles in the range
between 0.degree. and 90.degree. with respect to the main optical
direction 100 (wherein the origin of this angular referential being
defined by the intersection between the main optical axis 100 and
the surface on which the LEDs are fixed to). FIGS. 3, 4 and 5 show
an lighting device 40 where the light-modifying elements 32 are
respectively at 0.degree., 45.degree. and 90.degree. with respect
to the main optical direction 100.
[0097] In a particular embodiment shown in FIG. 6, the
light-modifying member 30 has a thickness "t", this thickness being
taken parallel to the main optical axis 100. Preferably
<<t>> is chosen significantly smaller than "h" to avoid
intercepting too many rays and thus reducing the impact on the
system efficiency.
[0098] In another particular embodiment, shown in FIGS. 7A and 7B,
the light source assembly 10 is a array of a plurality of LEDs 11,
each equally spaced apart by a distance "h", each LEDs having a
size of "e". The light-modifying member 30 is arranged such that at
least a part of the light-modifying elements 32 are spaced apart by
a distance equal, similar to or close to "e" and have a length
equal, similar to or close to "h".
[0099] A consequence of the presence of this kind of
light-modifying member 30 in the lighting device 40 is not only the
smoothness of the light cut-off but also the disappearance of the
light steps in the light-cut region, explained as follows in view
of the FIG. 9A to 9C (which show a top perspective view of the same
lighting device 40 but at, respectively, three different view
angles or directions with respect to the main optical direction
100):
[0100] Without the light-modifying member 30, the first edge 21
(not shown in FIG. 9A to 9C) of the reflector 20 hides suddenly (i)
the first line of LEDs 11 of the array of LEDs at a direction
located between the direction of FIG. 9A and the direction of FIG.
9B; (ii) the second line of LEDs 11 of the array of LEDs at a
direction located between the direction of FIG. 9B and the
direction of FIG. 9C; and (iii) the third line of LEDs 11 of the
array of LEDs at a direction located beyond the direction of FIG.
9C. These three events lead, respectively, to the three light
cut-off 4, 5 and 6 (see curve 1 of FIG. 10B) in the light cut-off
region 3, and to unpleasant light steps in the light cut-off
region.
[0101] Now, the provision of said light-modifying member 30 in the
lighting device 10, as depicted in FIG. 9A through 9C, allows a
transition between successive lines or LEDs when the view angle (or
direction) changes, by preventing progressively less and less
non-reflected light emitted from a line of LEDs 11 to pass close to
the first edge 21 when the view angle (or the direction) with
respect to the main optical direction 100 becomes less and less
important. This progression is depicted by FIG. 8, wherein: [0102]
FIG. 8(a), 8(b), 8(c) represent the vision of the lighting device
40 at, respectively, three different directions (or view angles),
progressively closer and closer to the main optical direction 100,
at a first latitude around the main optical axis 100; [0103] FIG.
8(d), 8(e), 8(f) represent the vision of the lighting device 40 at,
respectively, three different directions (or view angles),
progressively closer and closer to the main optical direction 100,
at a second latitude around the main optical axis 100; [0104] FIG.
8(g), 8(h), 8(i) represent the vision of the lighting device 40 at,
respectively, three different directions (or view angles),
progressively closer and closer to the main optical direction 100,
at a third latitude around the main optical axis 100; [0105] FIG.
8(j), 8(k), 8(l) represent the vision of the lighting device 40 at,
respectively, three different directions (or view angles),
progressively closer and closer to the main optical direction 100,
at a fourth latitude around the main optical direction 100.
[0106] Now, if the four visions of the light device 40, at each
latitude, are compared one to the other, it can be noticed that the
visible area of LEDs (i.e. not hidden by the light-modifying
elements 32) becomes progressively higher when the directions
become closer to the main optical direction 100. This means that,
in the light cut-off region, there are progressively more
non-reflected light rays going out the reflector 20.
[0107] This leads to such a smoothness of the light cut-offs 4, 5
and 6 that these light cut-offs disappear (see the resulting curve
2 of FIG. 10B--obtained with the light-modifying member 30--in
comparison with curve 1 of FIG. 10B--obtained without the
light-modifying member 30).
[0108] In a more particular embodiment of the invention, the area
of at least a part of the light-emitting elements 32 are defined as
being equal or similar to the area the adjacent gaps 39.
[0109] The lighting consequence is depicted by FIG. 8, wherein:
[0110] FIGS. 8(a), 8(d), 8(g) and 8(j) represent the vision of the
lighting device 40 at a first direction (or first view angle) with
respect to the main optical direction 100, at respectively four
different latitudes around the main optical axis 100; [0111] FIGS.
8(b), 8(e), 8(h) and 8(k) represent the vision of the lighting
device 40 at a second direction (or second view angle) with respect
to the main optical direction 100, at respectively four different
latitudes around the main optical axis 100; and [0112] FIGS. 8(c),
8(f), 8(i) and 8(l) represent the vision of the lighting device 40
at a third direction (or third view angle) with respect to the main
optical direction 100, at respectively four different positions
latitudes around the main optical axis 100.
[0113] Now, if the three visions of the lighting device 40 are
compared one to the other for each direction, it can be noticed
that the visible area of LEDs (i.e. not hidden by the
light-modifying elements 32) are similar from one latitude to
another latitude around main optical axis 100. This means that the
light remains homogeneous around the lighting device 40 at a fixed
direction, whatever the position around the lighting device 40 is.
The result is a well-balanced lighting on the area to
illuminate.
[0114] Alternatively, the area and gaps between the light-modifying
elements may be chosen differently in order to reach a determined
lighting effect.
[0115] While the invention has been illustrated and described in
detail in the drawings and foregoing description, such illustration
and description are to be considered illustrative or exemplary and
not restrictive; the invention is not limited to the disclosed
embodiments.
[0116] For example, it is possible to operate the invention in an
embodiment wherein the first edge 21 is not round and the LED array
is square, but the first edge is a square and the LEDs are arranged
in round or any other configuration. Moreover, the light-modifying
elements are not necessarily triangular but can have other kinds of
shapes.
[0117] Also, the invention is not necessarily limited to a lighting
device 40 with a plurality of light sources, but also relates to
lighting device 40 having only one light source (e.g. one LED). In
particular, the quantity of non-reflected rays emitted by this
light source over a first direction may be significantly lower than
the quantity of non-reflected light emitted by the same light
source over a second direction, and wherein a light cut-out exists
between these two directions: thus, the second edge 31 of the light
modifying member 30 may be designed to smooth progressively this
light cut-off.
[0118] Other variations to the disclosed embodiments can be
understood and effected by those skilled in the art in practicing
the claimed invention, from a study of the drawings, the
disclosure, and the appended claims. In the claims, the word
"comprising" does not exclude other elements or steps, and the
indefinite article "a" or "an" does not exclude a plurality. A
single processor or other unit may fulfill the functions of several
items recited in the claims. The mere fact that certain measures
are recited in mutually different dependent claims does not
indicate that a combination of these measured cannot be used to
advantage. A computer program may be stored/distributed on a
suitable medium, such as an optical storage medium or a solid-state
medium supplied together with or as part of other hardware, but may
also be distributed in other forms, such as via the Internet or
other wired or wireless telecommunication systems. Any reference
signs in the claims should not be construed as limiting the
scope.
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